We examine the issues and methods involved in evaluating the size that an equity fund might attain before it becomes unable to create additional value for investors. We discuss how capacity is defined, identify ten drivers and outline methods for conducting capacity analysis. We detail models that predict capacity, assuming that a fund adjusts the manner in which it trades and constructs portfolios as funds under management grow. We also provide an overview of transaction cost modelling, which is integral to predicting capacity. This study is primarily intended as an aid for investment industry participants who wish to evaluate the capacity associated with a given investment signal.